In storage apparatus, the configurations of storage apparatuses are designed, particularly focusing on the performance, considering how the storage apparatuses are used by users. This process is referred to as capacity planning (refer to Japanese Laid-open Patent Publication No. 2008-242872, for example).
Specifically, possible causes of slowdowns of the storage apparatus due to sudden loads are analyzed, and the configurations of the storage apparatuses are defined considering mid- and/or long-term load deviations. For example, in a pre-deployment capacity planning for a storage apparatus, the performance and capacity of that storage apparatus are defined.
Even when capacity planning is carried out, however, the performance and/or capacity of a storage apparatus may be turned out to be insufficient after the operation is started. In such a case, capacity planning is carried out again, and system or customer engineers manually modify the configuration of the storage apparatus based on the capacity planning. The storage apparatus is stopped during the configuration modification, which incurs down time of the system.
Generally, input/output (IO) accesses to a storage apparatus tend to be intensive on particular portions of a volume. Such portions are referred to as hot spots. Some hot spots appear in certain portions, while others wander across the volume from day to day. Such a wandering-type hot spot reaches its peak load which is about ten times higher than the average load, and the peak often lasts for about three to five hours.
Further, in some operations, a load may suddenly soar on a particular portion in a storage apparatus (such a sudden upsurge is referred to as a spike).
In conventional storage apparatuses, in order to ensure performance margin for accommodating the peak load of a hot spot, a capacity or performance margin kept by providing spare disks and/or using higher-performance disks, whereby improving the performances of the storage apparatus as a whole.
Further, although such a margin improves the performances of the storage apparatus as a whole, it incurs an additional cost for spare disks or overdesigned performance disks. Further, an unexpectedly high load still may occur, which cannot be addressed swiftly.
The performance of the storage apparatus may deteriorate if a certain portion in a volume is overloaded.